Translator for digital code group signals



July 26, 1955 LIPPEL ET AL 2,714,204

TRANSLATOR FOR DIGITAL CODE GROUP SIGNALS Original Filed April 3, 1951 2 Sheets-Sheet l FLASH PULSE GENERATOR PROGRAM PULSE GENERATOR INVENTOR.

BERNARD LIPPEL JOSEPH A. BUEGLER July 26, 1955 B, LIPPEL ET AL TRANSLATOR FOR DIGITAL CODE GROUP SIGNALS 2 Sheets-Sheet 2 Original Filed April 3, 1951 INVENTORS, BERNARD LIPPEL JOSEPH A. BUEGLER in the rings, is received by tie photocells 24. It will be clear by referring to Figs. 4 and 5, that the particular photocells which are actuated by light passing through the wheel will depend upon the Wheel position and that for our illustration of five digit encoding there are 3'2 different digit signal combinations which may be generated. The photo elements 17 are coupled by parallel channels to the input of D.-C. amplifiers collectivel labeled 54- and the output of each amplifier 54 is coupled to the input of a bistable multivibrator or fiip-fiop unit, the five units being labeled collectively 55.

The outputs of the units 55 are coupled in order to the control elements of electron tube amplifiers 46, 47, 48, 49 and 50 and the cathode element of each amplifier tube is connected to ground through the solenoid of a corresponding relay switch 41, 4-2, 43, 44 and 45 of translator 12. The relay switches are each of the double pole, double throw type normally in the down position as has been shown.

Prior to each reading, that is, each flash of light from tube 23, a clear pulse from program generator 20 is simultaneously applied to each of the flip-flop units 55 by the connection shown to restore them to an initial operating position.

Consider now the operation of the system thus far described. The cycle of operation which is periodically repeated is, first, the illumination of a narrow sector of wheel 11 for a short time interval efiectively to actuate the exposed photocells 24- and so to read an instantaneous position of shaft 10. disk or the Wheel which is exposed through openings in the coating 22 is such that reading from top to bottom the first, second and fourth of the five photocells 54 receive light and the output of each is indicated as a negative pulse. parent portions of the opaque coating 22 are in cyclic binary code corresponding to the arrangement shown in Fig. 4. It will be clear from an inspection of this figure that the sector of the wheel being exposed or sampled is the sector nineteen, which in cyclic binary code is written as 11010. The wave forms shown at the outputs of the first, second and fourth D.-C. amplifiers 54, which correspond to the first, second and fourth positions of the binary number, indicate the transmission of a pulse,

shown on the drawing as a positive pulse, to the input I of the first, second and fourth amplifier flip-flop units 55. The units 55 are assumed to be biased or conditioned by the earlier occurrence of a clear pulse so that the output .of each unit is of low value here referred to as zero out- In the drawing, the sector of the It is here assumed that the coded or transput. The application of a positive pulse at the input of any unit will reverse this condition to provide a maximum output, here shown and referred to as a positive output or a digit signal output and this output will remain until a clear pulse restores all units to the initial condition. Thus in the drawing for sampling of sector nineteen an output is provided only at the control grids of tubes 46, 47 and 49 and the storage or maintenance of the signals on these grids is indicated by the wave form diagrams of relatively long pulses which endure until the occurrence of the clear pulse as indicated by the dotted trailing edge of the pulses. Since the solenoids or relay control elements for the translator switches 4145 are included in the cathode circuits of tubes ease, and the flip-flop units 55 are directly coupled to their control grids, the operation is to register all generated digit signals simultaneously and in parallel channels. Directly coupled here means that the connections of the units 55 to the plurality of vacuum tubes 46-50 are D.-C. connections and the cathode circuits of these tubes therefore hold in storage or in register the sampled data in the form of digit signals in parallel channels.

Since the operation above described is repeated periodically at the chosen repetition rate of generator 20, it will be clear that the arrangement operates to encode in parallel channels the analogue values, that is, the posi A. tion of shaft 10 as digital code group signals in cyclic binary code. The encoding member is the disk 22 having the coating 12 with transparent portions arranged in accordance with Fig. 4 of the drawing. The coding or commutating elements of the wheel therefore comprise five rows of commutating elements which are divided in the direction of rotation into 2 or 32 sectors. The program generator 20 operating flash lamp 23 via the generator 51, provides means operative during recurrent intervals at a chosen sampling rate for coupling between the index member or reading head 24 and the commutating elements within a narrow indexing width which should not exceed the width of a sector. The pick-up elements 24 and the associated output units described comprise means responsive to the coupling for generating and registering simultaneously and in five parallel channels the digit signals of a five-digit binary number which represents the instantaneous relative positions of the encoding wheel and the index head 18.

The advantages of employing cyclic code for the encoding process have been recited in the aforementioned patent application. A principal advantage of cyclic code for encoding analogue data relates to the fact that with cyclic binary code the change from one number to the next requires a change of only one digit in the binary number. This will be evident when we consider and compare the wheel arrangements of Figs. 3 and 4. It will be noted that with the standard binary code, more than one digit may change in moving from one sector to the next adjacent one. For example, a change from the sector thirty one to sector Zero requires a change of all five digits. Conversely, in the cyclic code arrangement of Fig. 4, at no place around the circle is there a change of more than one digit. When cyclic code is employed, a slight misalignment of the reading head 18 can ordinarily cause a maximum error of only one sector while if standard code were employed, a slight misalignment might produce a signal designating a sector many sectors removed from the correct one.

For other processes in the system, such as comparison of digit number signals and for decoding the digit signals to produce analogue values, the standard binary code is readily employed whereas the cyclic code cannot be directly used without unduly complicated additional apparatus. Accordingly, the translator operates to change the digit signals of the output cyclic code number simultaneously and in parallel channels to digit signals of stand ard binary code by means of the relay operated switching circuit shown within the block labeled 12.

The principle of translation is as follows: Consider translating the number 13 cyclic, which is 11011, to 18 standard, which is 10010. The rule which can be developed for any number is to reverse all digits following a one, and repeat this operation successively. Therefore, we may write this operation as follows:

(a) 18 cyclic: l-l-Gll- (b) =1099 (o) =100ii (d) =10010=18 standard The presence of a one in the first digit position of (a) required all digits in subsequent positions to be reversed to give (b); the presence of a one in the second position of (4:) also required reversal of subsequent position digits to give (0); the presence of a one in the fourth position of (a) required reversal of the subsequent position to give ((1); there being no positions subsequent to the fifth, no reversal operation is required for the presence of a one in the fifth position of (a).

Similarly for the number 19, shown in the drawing, only the last switching step is different from that given in the example above for the number 18 and the switching operations of reversing all output positions subsequent to the occurrence of a one digit signal can be followed by inspection from left to right. It will be noted that the apparatus in translator unit 12 is arranged to perform the described reversals of digit signals simultaneously. A source of D.-C. potential is provided to which are connected in series the relay operated reversing switches 41-45, one for each digit position, except the last, which need be simply a single pole, double throw switch although a reversing switch has been shown. The input digit signal currents in the cathode circuits operate, each, its appointed switch and an output connection is provided from each switch position. Thus a parallel operation of all switches is effected and standard binary digit signals are produced at the output terminals, simultaneously and in parallel, for transmission to the appropriate unit in the system shown in the referred to patent application.

Considering now in more detail the operation of the cyclic to standard binary code translator 12, it should be remembered that the normal or unactuated position of the switches 41 to 45 is down. This would be the position of the switches if all of the it will be clear that for this condition (with the manual switch in the up position as shown in the drawing) there is no potential from source 39 supplied to any of the output binary terminals and accordingly the digit signal outputs are all US. This is the condition which should obtain, since the cyclic and standard binary codes are identical for the number zero. If now we assume that any switch, say the switch 42, is actuated by a 1 signal from amplifier 47, it will be clear that the two arms of the switch are thrown to the up position and potential from 39 is supplied to the output terminal of unit 42, i. e., the output is a l. The switch 42 by its actuation has, however, also supplied potential to the outputs of all of the following switch units 43 to 45. Accordingly it is clear that any input digit signal which actuates any one of the switch positions operates to reverse the output signal in all subsequent switch positions.

Consider now the specific case shown in the drawing for the translation of the number 19 from cyclic to standard binary code. To understand what occurs, the operation, which actually is a parallel simultaneous one may most conveniently be envisioned as a sequence of operations starting at the left with the most significant digit and with the assumption that all switches 41 to are initially in the down position so that all outputs initially provide zero output potential. The input digit signals for actuating the relay switches are now to be considered as applied in order from left to right and to endure after being applied. Accordingly, switch 41 is actuated or thrown to the up position since the input digit signal is a l, and therefore, if nothing further occurred, all outputs would be ls. Next switch 42 is actuated to the up position and accordingly its output is changed from a l to a O, and likewise the outputs of switches 43, 44 and 45 change from ls back to Os. The digit signal to switch 43 is a 0. Hence 43 is not actuated and no outputs are changed. The next digit signal is a l which actuatcs switch 44. Hence the output of 44 is changed from a 0 to a l, and the output of subsequent switch 45 also changes to a 1. The last digit signal is a O and therefore no actuation of the switch 45 occurs and its output remains a 1. Accordingly the outputs from left to right are 10011 which represents the number 19 in standard binary code.

It will be clear from the above description that the actuation of any switch reverses the outputs of all subsequent switches. It will also be evident that the several switches 41 to 45 are reversing means connected in series to the source of potential 39 whereby an input digital sig mat in any position reverses the output signals in all subsequent positions. The description of operation given above follows the principle of translation stated in the paragraphs in column 4, lines -70.

Another point of view which perhaps more clearly explains the operation of translation makes it unnecessary to consider the sequence of reversing operations described input signals were Os and above. This other point of view is to consider each switch position as a complete digit signal translating unit which operates in accordance with any actuating input signal and the condition of operation of the preceding switch at its left. From this point of view the apparatus of the translator is comprised of the plurality of switching units 41 to 45 one for each position of the five digit code group here used for illustration. The first switching unit 41 corresponds to the most significant digit of the group and the subsequent units 42 to 45 correspond, in descending order, to less significant digits. The connections from the amplifiers, 46 to 55), to the switch solenoids provide means for applying an input digit signal to each of the switching units. The output terminals, labeled binary, provide means for deriving an output digital signal from each of the units. Each of the subsequent switching units 42 to 45 are connected or coupled each to the preceding unit to its left. Accordingly when any one of the switching units 42 to 45 is actuated by an input digit signal Which is a l, the output of the particular unit will be a l or a 0 depending upon the condition of operation of the next preceding unit at its left. Thus, if the output of the preceding unit at the left of the particular switch being considered is a l, the output of the particular switch will be a 1 unless it is actuated. If it is actuated by an input signal the output will change from a l to a 0. Accordingly, it will be clear that the input digit signal to a particular unit is, in effect, compared with the digit signal output of the preceding unit. If actuated, its output is a 1 if the preceding switch output is a 0. Likewise, the output of a given switch will be a I if it is not actuated but the output of the preceding switch is a 1. For other conditions the output of the particular switch will be a 0.

Since the output of any particular switch depends upon two input conditions, the actuating signal and the condition of operation of the preceding switch, such an arrangement is sometimes referred to as a logical not and circuit. Such a circuit produces an output when one or the other of two input circuits is energized but produces no output when both or neither of the input circuits are energized. From this point of view the arrangement may be considered as a sequence of not ant circuits. Accordingly it may be stated that each of the subsequent switching units 42 to 45 comprise means which are responsive to the input digit signal applied thereto and to a condition of operation of the next preceding switch unit for producing an output digit signal.

The first switch unit 41 will always produce a 1 output, when it is actuated by a 1 input. This is shown in the example labeled in the drawing where the input number is 11010. Switch 41 which corresponds to the most significant digit is actuated so that its output is a l. Continuing to view the operation from this point of view, switch 42 is also actuated by a 1 input signal but is also responsive to the condition of operation of the preceding switch 4?. which makes its output a 0. Switch 43 is unactuated since the input signal is a Zero. However the condition of the preceding switch 42 is such that its output is a 0. Similarly switch 44 is actuated by a 1 input signal but since the output of switch 43 is a 0 the output of switch 44 is a 1. Finally at the input of switch 45 the digit signal is a 0, hence the switch is not actuated. But switch 44 has a 1 output signal and accordingly the output of switch 45 is also a l.

The code wheel shown in Fig. 5 is a drawing to somewhat reduced size of a coding wheel which has been employed in practice for encoding angular data in cyclic binary code numbers having 10 digits. The Wheel is, accordingly, divided into 2 sectors of 0.0ll, the total number of sectors being 1024. The sectors 1022, 1023,

Zero and l have been labeled on the drawing to indicate the fineness of the divisions.

It will be evident that with a disk having this many divisions, or disks having a higher number as may be reof aligning a corquired for some services, the problem responding number of photocell elements will require the use of very small cells or some method of spacing them because of their physical size. In practice, it has been found preferable to arrange all the cells to be effectively along a radial line by providing optical elements which transmit the light from the sampling apertures 56 to the photocells positioned away from the reading line.

An alternative arrangement is illustrated in U. S. Patent 2,590,110, entitled System for Producing an Encoding Device, which was filed concurrently herewith in the name of Bernard Lippei and assigned to the same assignee, the Government of the United States. As disclosed in that application, two difierent reading heads may be employed set relative to each other at an arbitrary angle. For this type of indexing arrangement it will be evident that the disk must be made in a corresponding manner so that the commutating segments are staggered in accordance to the way they are to be read in operation.

In the drawing of Fig. l, the translator unit for con verting from cyclic binary code to standard binary code has been indicated as having a cyclic input number 11010 and a standard output number .0011, so labeled on the drawing. The D.-C. source 39 is connected by switch 40 in the up position shown, to provide this result. If, however, the switch it) is thrown to the down position, the standard binary output digit signals are each reversed so that the reversed binary member will be 01100. The use of the reversed binary number is disclosed in the first mentioned pending application above referred to and so will not be further discussed here.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. Apparatus for parallel translation of digital code group signals from cyclic binary to standard binary code, comprising a plurality of relay operating switching units, one for each digit position of the group, the first of said units corresponding to the most significant digit and the subsequent units corresponding in descending order to less significant digits, means for simultaneously applying I an input digit signal to each of said units for actuating each relay, means for simultaneously deriving an output digit signal from each of said units, a source of potential, means for coupling said source to said first unit, means coupling each of said subsequent units to the next preceding unit and thereby to said source, each of said subsequent units comprising means responsive to the input digit signal appiled thereto and to a condition of operation of said next preceding unit for coupling to said source to produce an output digit signal.

2. Apparatus in accordance with claim 1 which further comprises means for switching said means coupling said source to said first unit to reverse all output digit signals.

References Cited in the file of this patent UNlTED STATES PATENTS 

